Aquatic Ape ... Theory? Hypothesis?

It was first introduced to me about 10 years ago in a class on Asian Religion and Philosophy. For the first 3 weeks of the class, the professor never even touched Asia; just went over human evolution and migration across the continents. That was the first bit of coolness of that class, the idea being to get us deep into the mindset of where these people lived, how they got there, their probable background, the geology and climate, etc.

During the evolution bit she introduced Aquatic Ape theory as a "Something to think about/think outside the box" type exercise. I was especially intrigued by the politics behind how the idea was presented to the world at large and that the biggest complaints weren't necessarily reasons why the hypothesis can't work, but more along the lines of old men who didn't want to have to rewrite their textbooks. I also called my activist-feminist parents to complain that I'd never heard of Elaine Morgan and "Descent of Woman." I remember us having a copy of "Ascent of Man" in the things-we-hope-our-kids-will-pick-up section of the house. Mom and dad apologized; thought they had "Descent of Woman" in there too.

It came up again in my current Physical Anthropology class. Professor asked a few of us to volunteer to spend last weekend researching it and put together a presentation for the rest of the class. I very eagerly did so, since it was going to be my final project for the class. Downside: Now I need a new topic for my final.

Anyhow, the more I read up on it, the more I like the theory. It feels like it explains many of the differences between us and other primates so much better than "We moved to the savannah and simply, randomly, stood up/lost our fur/got fat/dropped our larynx/learned to hold our breath/etc.

Honestly, I feel with a lot of long-held theories, they tended to be looked upon as much more simplistic than they really are. E.g.; we once had this image of human evolution as a nice, neat, linear process. A evolved into B, evolved into C, and finally H. Now we know it's more like many, many tiny branches of hominids, most all of whom died out and we 'won' so to speak. I suspect that if even if AAT becomes widely accepted, it too is only one piece of a much larger and ever more complex evolutionary puzzle.

Replies to This Discussion

I have considered this explanation for a long time and it doesn't pass the test, sorry (I've actually a physical anthropologist degree). I'm inclined to consider some wading in our evolution, but not at the degree the aquatic ape implies.

Just a thought, where did we swim so much? Almost every lake, pond or river in Africa is infested with cocodriles, of the big kind. And that's the least serious objection that one can made to it.

I don't remember all the points of the aquatic ape in detail, would you write them down so I can clarify them for you?

I have a list of human evolution hypothesis with their authors and dates somewhere. If you want it I can find it.

I do think that women played a major role in our evolution, specially in our sociability. We are one of the few mammal species that seek help in the time of labor. We have had some important problems in our evolution related to carrying babies (hard problem being bipeds), babies increasing size (labor problems, energy problems, breast feeding problems, food gathering problems) longer labors and closer pregnancies (more carrying, energy, food, etc, etc, problems). Even with the help of men (I'm sure they did help, not everything has being the patriarchal "women are things" stuff in our history), dealing with all that problems was our doing and so they were their evolutionary consequences.

About our hair thinning (we've never lost it, we have as much hair as chimps): I know it's not how most anthropologists see it, but I tend to see more like a metabolic consequence of the large amount of fat we have when we're born, with it's an adaptation to our energy need for our big brain as babies (white fat, the increased fat we have as newborns and until six months old, is a very bad insulator and it's not of the same kind marine mammals have; one of the points of the aquatic ape), but we don't understand hair growth enough yet to make such affirmation.

I just joined A/N a few days ago and saw this post; it's something I have some expertise on. I've been researching the evidence surrounding the "aquatic ape" idea for over a decade now to determine whether it's accurate, honest, and makes sense in terms of evolutionary theory. (Bottom line: it doesn't.) There are a number of reasons, and I could go over any specific points you'd like to get into, but you may be able to find the information you need on my website, which I first put online in 1996, and which I've updated over the years. My site has been used as a source for The Straight Dope, the Fortean Times, and lately a fair number of college courses; I've also written the entry on the subject for the (way expensive) Sage Encyclopedia of Anthropology. The website is at .

This statement of yours is common with people who've read what the proponents of the idea write:

Anyhow, the more I read up on it, the more I like the theory. It feels like it explains many of the differences between us and other primates so much better than "We moved to the savannah and simply, randomly, stood up/lost our fur/got fat/dropped our larynx/learned to hold our breath/etc.

And the reason it seems to explain those things so much better is that the quoted bit is nothing like real mainstream anthropological ideas; it's what the proponents of the aquatic ape idea inaccurately claim is anthro's idea. In other words, it's a strawman. That's not your fault; you're curious about the subject and in return for your interest they mislead you. I don't think that's fair to do to someone who, like you, simply wants to learn more about our past.

BTW, if you're looking for a treatment of human evolution that deals with females and children and their central role in our early past, you could do worse than read my late wife Nancy Tanner's 1981 book On Becoming Human. It's getting on now and there's lots of newer info in the field, but virtually all of it furthers supports what Nancy suggested in that book, for instance the info about chimps hunting with tools that was observed a year or so ago. Interesting that predominately that tool use for hunting was done by females, just as other chimp tool use is done most often and for longer by females, who also have been observed teaching tool use to their offspring. (It's not that the males are dumber or less handy, just less nutritionally stressed; they don't need to use tools as often, so they don't.) In fact the field of paleoanthropology has incorporated a lot of what women have done on the subject over the past 40 years; they've been some of the major players, people like Thelma Rowell, Shirley Strum, Sally Slocum, Jane Lancaster, Adrienne Zihlman, Nancy Tanner and others. Sadly, Elaine Morgan, despite her claim to feminism, has consistently ignored these women's work, perhaps because it conflicts with her self-authored myth about her "battle" against male-dominated orthodoxy.

Let me quickly and briefly demonstrate what I mean by the strawman account regarding the features you mention above ("stood up/lost our fur/got fat/dropped our larynx/learned to hold our breath"):

1) stood up

For a long time there was an argument about whether or not the last common ancestor of African apes and hominins was a knucklewalker or bipedal; it's clear now, especially with the analysis of "Ardi" (Ardipithecus ramidus) that as early as we find hominins they are bipedal. IT's also clear that there are advantages in being bipedal as well as disadvantages, and what this means is something that people are usually uncomfortable with. Namely, it could simply be a lucky accident for us. That is, we seem to have retained some primitive traits (our relatively large and numerous sebaceous glands are one, bipedalism is another) while African apes changed more from that while we just refined the traits. This is unlike the old way of thinking that dominated the early half of the last century and earlier. I also talk about it a bit more on my site, on the summary page, under the heading "The unpopular role of luck in evolution".

2) lost our fur

As Malena pointed out, saying we "lost our fur" (or more accurately, hair, is inaccurate and therefore trying to answer that means you can't get a right answer, since the wrong question is being asked. :) But what we have is shorter and finer hair than African apes, except for longer hair on our heads. Part of this is due to sexual selection, as you can see by when and where you see the changes in our hair. They vary a lot between the sexes, change right at puberty, and also vary between peoples to some degree. That's classic sexual selection, unlike the environmental idea of the aquatic idea. But this shorter hair does have some advantages in some environments, especially hot and dry, where it alolows sweat to evaporate nearer the skin, and basic physics tells us (and experimental data shows us) that this makes for more efficient sweatcooling.

On the aquatic side, hairlessness is actually very rare among aquatic and semiaquatic mammals. I have a page specifically on those mammals and this subject. Bottom line: except for the hippo, whose hairlessness is easily seen as due to the well understood problem of large animals getting rid of heat, the only mammals which have lost hair and are aquatic are fully aquatic and have been for tens of millions of years, far longer than hominins of any kind have existed. The hair (or lack of it) in those species is also the same for both sexes and doesn't change over their lifetimes, very unlike ours.

3) got fat

Our fat, according to the best expert on the subject (Caroline Pond), is like that of other primates. And humans vary a lot in this; we make a mistake when we examine just "Western" peoples. Many herding or gathering/hunting peoples are about as fat as many macaques, for instance. But in general humans are fatter than other primates, or lots of other mammals, but it's important to note that non-human primates who are allowed to eat as much as they want get very fat just like we do and in the same places (unlike what the proponents of the aquatic idea typically claim). The key to this is predation, avoiding predation, and I cover that on my site too. ()

4) dropped our larynx

This is something where there's been new info in the past 20 years that's really interesting, but you should note that this has never been a good piece of data for the idea. (my page on that: ) It turns out that a descended larynx is a common feature of many animals, including chimpanzees, but earlier studies didn't show this because they were done on dead animals via dissection. With MRIs being easier to do it's been possible to study this in living animals, so new info. It's on that page I just linked.

5) learned to hold our breath

This is twofold; first, it's vastly overstated by aquatic proponents. Lots of animals can hold their breath just fine; in fact they'd drown if they didn't and tried swimming underwater. But various monkeys can and do swim and dive -- they hold their breath -- and untrained dogs actually can hold their breath somewhat longer than untrained humans. But we do have better fine control of our conscious breathing, and this is a side benefit from our being bipedal. In quadrupedal mammals the muscles around their lungs are used by the forelimbs for locomotion, and this means they have less conscious control of those muscles available for breathing. We have that ability to a greater degree because we're bipedal. It's a lucky break, since this turned out to be very helpful for better vocal communication, and eventual speech, but happened for different reasons entirely. Evolution is funny that way.

Anyway, if you have any questions at all you could either post here (I'll check back sometimes although we will be travelling in about a week), or at my page here at A/N, or through email feedback via the mailto links on my site (at the bottom of most every page). I hope I've been helpful.

Excellent explanation!
Good you mentioned Caroline Pond, she is probably the only expert in subcutaneus fat that there is.
What do you think about newborns fat? Caroline Pond made the point that brown fat is for heating and human babies has the expected amount of it for any newborn primate. I made the point that white fat (that it's very energetic) it's for the brain, because that's the conclusion I reached after study several theories about the subject. Babies fat growths until around six months when it starts to decrease, different population may have different times but it's usually about six months (I did search for hunter gatherers statistics), and the thing about this it's about the time when the baby gets to big for human milk to supply all the energy he or she needs (based on estimations on how much milk a woman can produce). And babies need great amounts of energy because two things, they are bigger than other primates (even gorillas at that age) and they have very big brains (I wouldn't say bigger brains, human babies seem to have the expected size for a baby primate that size; adults, we are the ones who don't follow the expected). And brain is a very sensitive organ about energy. My jury (this was for my master dissertation) was composed for several woman who believe that the mother can always supply for her children and got kind of confused when I said that, but even if women can change the amount of milk they produced, there're limits. Milk production takes time and energy for the body, we have to reach a point we cannot produce enough no matter how much we eat, how fast is our metabolism and how much time the baby is suckling.

For quite some time it was thought -- really more assumed, which is always a mistake in science -- that brain growth was a primary reason for human infants' fat, which is pretty much unique in mammals. But it's not actually that. There was a very good paper by Christopher Kuzawa ("Adipose Tissue in Human Infancy and Childhood: An
Evolutionary Perspective" in YEARBOOK OF PHYSICAL ANTHROPOLOGY 41:177–209, 1998); Kuzawa finds no evidence that brain growth per se is behind infant fat (I had thought so too before reading his paper). He shows it as a buffer providing nutrition during lean times and illness. Here's an excerpt explaining it better:

"Evidence is presented that fat stores are mobilized during infections, hinting at one possible mechanism underlying the association between nutritional status and infectious morbidity and mortality among infants in nutritionally stressed human populations. Consistent with the proposed hypothesis, well-fed infants acquire peak fat reserves by an age of peak prevalence of malnutrition, infectious disease, and fat reserve depletion in less-buffered contexts, and childhood—characterized by minimal investment in the tissue—is a stage of reduced risk of energy stress."

BTW, that paper is available free online as a PDF ()

And Pond is great; she really started the ball rolling on modern studies of fat, and especially on the evolutionary significance of fat. She's got a good book on it too, The Fats of Life, which is one of those pop but scientific easy to read things that don't come along often enough.

I know the paper. I have several objections to it. One, not well fead infants, but all infants adquire that peak fat reserves. The malnutrition has to be really acute for this not happening, usually because of a disease or a really neglected child. If the child is breastfeed, even is the mother is malnourished, the child will increase the white fat content (the fat won't be exactly the same because fat tissues vary with the mother's milk "quality").
Yes, the energy requirement has to do with the general size of the baby, but the organ that needs this buffer the most and it's using the baby reserves the most, is the brain.

I actually joined up because I noticed Jo's post on one of my interests.

Yes, hair changes for cooling efficiency plus sexual selection. It's coupled with more eccrine sweat glands, which are what allow us to use persistence hunting as you describe. What happens there is that we have lots of eccrine sweat glands, unusual except for some savanna primates like the patas monkey and the vervet (who are good runners). Most other animals have mostly all apocrine sweat glands. Both work just dandy, for about 20 minutes. But aprocrine sweat glands work by building up fluid in the glands and then using that fluid; it runs out in 20 minutes or so and the gland has to recharge, so they can't keep sweatcooling at the same rate without a resting period. Eccrine sweat glands, OTOH, just pass through fluid so they can keep going as long as you have water in the body. This does mean you need water, but in practice this isn't much of a problem. For instance, the !Kung would go on daylong hunts without carrying water, and during that time they'd only get water -- if at all -- in ways that even chimps have been observed getting water, so it's something our ancestors could've done too. And the !Kung did that in much drier areas than our early ancestors lived (and at least as hot). So that need for extra water is a theoretical problem but not so much a problem in reality.

But you don't need that emphasis on hunting; persistence hunting was likely not done for millions of years for hominins (probably not until Homo erectus at least). Just walking about gathering iwould provide plenty of selection. Another point there is something Peter Wheeler studied, and measured, in work done in the 1990s: just being upright is goood for cooling in hot sun. First, you have less surface area getting hit directly by rays, but also (and I hadn't thought of this at all until Wheeler pointed it out -- duh) the temperature nearer the ground, under a hot sun, is higher than it is even a few feet above the surface, because you have that big partly reflective heatsink emananting heat. As he described in a BBC documentary:

"I've just set up two identical temperature sensors here. The one on the left has been placed close to the ground surface in the shade and the right one some six feet above it in this small acacia bush, also in the shade. And as we can see there's some considerable difference in the readings of the two sensors. [clip one sensor reading 44.62, the other 27.02] The one near the ground is reaching temperatures almost 20 degrees centigrade higher than the more elevated one. What bipedalism is doing is it's moving more of body surfaces further away from that hot ground and placing them in these cooler and faster moving air streams where more heat will be carried away from the body by the process of convection."

That's a big difference; I was surprised it would be that large.

And although there would be some division of labor between the sexes even for very early hominins, I think it's often overstated. (That info about chimps hunting with tools that was observed a year or so ago that I mentioned above, mostly done by females, supports this.) And it's important to remember that even among modern gathering and hunting peoples it's not that clearcut. In most groups there is a division between gathering and hunting, hunting done by males and gathering by females and sometimes kids helping. But hunters, especially when returning empty-handed, don't spurn picking up some veggies on the way home, and gatherers who come across a "gettable" animal aren't going to say "hey, that's not my job" and leave it there.

Actually there are a variety of ideas among various aquatic proponents about the time period in question; the biggest problem with that is that over the past few decades they've gotten more vague about that and the extent of water use. They should be getting less and less vague as time goes on, like most science.

Yes, grubs and such have a nice supply of fat and they're easy to get, so they eat them. So do chimps. (In fact that's one of the major ways in which chimps use tools, and make tools and teach tool use to the kids, and like the other tool use for food it's done more often by females.) I would too if I was out there looking for food. And in fact a lot of people still eat them. When we're in Thailand they've got a variety of roasted bugs and grubs at the local market, and they're not eaten just by old folks into traditional foods. Even young folks, like young couples on a date, might pick up a bag of roasted crickets as a snack. (The same couple on another day might hit the Dairy Queen for an ice cream cone or Swenson's for a sundae.)

Being upright it's good for cooling only at noon! The worst hour for being under the sun. The rest of the day the sun rays are obliques and hit worse upright creatures. I know Wheeler paper, and is incredibly flawed. It doesn't look like, but it completely ignores physiological human reactions well established by medicine in the base of several populations, including the !Kung, decades before Wheeler works.
And that's not his worse work, in the paper about the "expensive tissue hypothesis", he supports his conclusions in the excellent hard work of Chivers and Hladik, who tried, with the material available, to compare primates digestive systems. But the sample (inside the bigger sample) that would allow to justify Wheeler views, is very small and is biased toward a group of very specialiced herviborous monkeys (being specialized is weird in primates in general), the colobus of the Presbytis genus. Most of the sample is from zoos and institutions, a terrible thing because digestive organs can change a lot due enviromental stress; and several animals, including the only hominoid available for Wheeler analysis (an orangutan), are juveniles. That makes all Wheeler (and Aiello) conclusions very badly supported. It took me a lot of effort to obtain Chivers and Hladik paper and, when I finally did, I couldn't believe my eyes. The paper is excellent, I only can imagine how hard it was to make all that dissection and meassure all that organs; but it doesn't support at all Wheeler's hyphotesis.
If you think I don't like Wheeler's work, you are right, I don't like people who justified their conclusions in biased and terribly uncompleted data like if it were good data.

I don't care for the expensive tissue hypothesis myself; like the dietary ideas which are found in the aquatic idea it's flawed, IMO.

As for upright posture exposing more body area to sun (except at noon), there's a problem with that too. It only works like that if the non-upright animal is facing the sun directly, or facing 180 degrees opposite. And the part about being further away from the hot earth still holds anytime. That said, there's clearly a sexual selection component there, and muddling the whole thing a lot is that hair characteristics can change quickly. There are studies with the coats of dogs showing that a lot of hair differences come down to only a few genes (3 genes seem to control all the variation in coat growth pattern, length, and curl in dogs), and there are other studies that suggest that this is true in mice and cats as well. More study on that is needed to be sure, but we know it's an easily changed because we can see since there are differences between human populations which haven't been separated for all that long in evolutionary timescales. The studies of lice to try to determine when hair characteristics changed are very interesting (and it's a clever way to try to figure that one out) but I'd like to see how all that shakes out rather than accept it as a done deal. The one thing we don't see is decent evidence that it would be due in any way to some degree of water use, as the aquatic idea claims, but it's a fascinating subject.

Thanks for your views on this and on Kuzawa's paper. It's always good to get another's perspective on things like that.

(And I'm with you on the data-gathering, ala Chivers and Hladik... or for that matter Pond and her colleagues. It's an immense amount of work. It'd be an immense amount of work even if you could easily order specimens delivered to your door! I'm always glad that there are people who'll dig into something like that.)

Yes, the data gathering part of the scientific work, is really hard and really important althought some schools (in social sciences specially) tend to disregard it. That's the reason I tend to find ethology more appealing than social anthropology (I have friends that would hate me for saying that; most social anthropologist actually hate ethologists).XD

There's something else about the upright posture being good for the life under the sun. We became bipeds long before living in the african savannas. We were bipeds in shaded forests. You said it before, is quite a primitive trait.

Do you know about Belyaev silver foxes? That was a fast change in fur and he was selecting for tameness!
Who knows, may be ancient human sexual selected something completly different that thin fur, but thin fur it's what they got.

Hair is such an easily changeable feature that -- I think -- we won't be able to even nail down what happened when until we can definitively say how it happens genetically and exactly when those changes happened. We're not there yet, and it may be a long time before we are (although we're starting to be able to figure out things like that). And like the lice DNA studies, it's probably going to start with a long period where the data is thought to be firmer and more exact than it is.

The study of domestication of foxes is one of the most interesting, partly due to the examples of "byproducts" of domestication (like the hair you mention, the ears -- folks who don't know about it can search, Wiki has a decent article on it, I think, with pointers to additional online material). I think there's a good case to be made for describing our evolution as self-domestication.